Wrench having a pivoted outer jaw



July 10, 1951 B. P. KUNZ 2,559,974

WRENCH HAVING A PIVOTED OUTER-JAY! Filed Nov. 5, 1949 x I JNVENTOR.

Bern'ard P. Kunz ATTORNEYS Patented July 10, I 9 51 WRENCH HAVING A PIVOTED OUTER J AW Bernard P. Kunz, Englewood, 0010.

Application November 5, 1949, Serial No. 125,672

1 Claim.

This invention relates to wrenches and moreparticularly the swinging jaw type which is automatically adjustable for use on different size work.

One of the objects of my invention is to produce an improved swinging jaw type of wrench which will be capable of efficiently gripping all sizes of work it is designed to receive between its jaw.

Another object is to produce a wrench of the.

type having a swinging jaw with right angular jaw faces and a cooperating fixed jaw with a circular jaw face which will have such a geometric relationship that efiicient gripping action will be possible on all sizes of work which can be engaged, yet such action will not be so intense that an undesirable crushing action may be caused to occur by a W applied force.

A more specific object is to so construct a wrench of the type above referred to which is so designed that the angle between the pivotal axis of the swinging jaw, the center of the gripped work and the center of the curvature of the fixed jaw face will always be within predetermined limits for any size of round work that can be received between the jaws.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in which:

Figure l is a side view of a head of a swinging jaw wrench embodying my invention, said figure showing the wrench gripping a size of round work approximately one-half maximum size for the wrench, and the geometric relationship existing under such conditions;

Figure 2 is a top view of the wrench; and

Figure 3 is another side view showing the wrench gripping approximately the largest possible round work and the geometric relationship existing under such conditions.

Referring to the drawings in detail, my improved wrench disclosed in the various figures comprises a handle member ID and a swinging or pivoted jaw member II. The handle member at one end has a hand gripping portion I2 (see Figure 2) and at its other end a jaw portion I3 to be referred to as the fixed jaw portion.

The swinging jaw member II is of general L-shaped form having a long leg portion I4 and a short leg portion I5. The free end of the long leg portion has a lateral extension I6 reduced in thickness and this extension portion fits into the end of a slot IT at the jaw portion end of the handle member and is pivoted to this jaw portion end by a pin I8. At the free end of the long portion I4 of the swinging jaw member is a. thumb engaging protuberance I9 to facilitate in opening up the swinging jaw member II.

The longer leg portion IA of the swinging jaw member is provided with a jaw face 20 and the shorter leg portion is provided with a jaw face 2|. These jaw faces are arranged to be preferably at right angles to each other although the relationship may be slightly varied within close limits. The two jaw faces are provided with teeth as shown for better gripping purposes.

The fixed jaw portion I3 on the end of the handle member and to which the swinging jaw member II is pivoted is provided with an outwardly curved jaw face 22, also provided with teeth for better gripping purposes. This curved jaw face 22 is constructed so that all of it will lie on a portion of a single circle, the center of which is at C and the radius of which is indicated at R. In other words, the face 22 has a single center of curvature and a single radius of curvature.

The three jaw faces 20, 2| and 22 all cooperate to hold various sizes of work such as those indicated at 23 in Figure 1 and at 24 in Figure 3. In order that the jaw faces may be automatically caused to engage with any work, a spring 25 is employed to bias the swinging jaw member toward the fixed jaw portion. This spring is positioned in the slot I? of the handle portion with one end fixed to the handle by a pin 26 and the other end connected by a flexible ribbon member 21 to the swinging jaw in the manner shown in Figure 1. 1

To have a practical and efficiently operating wrench of the type described, that is a wrench having a swinging jaw member with two faces at right angles to each other and cooperating with a curved jaw portion faced on the end of a handle and having a single radius of curvature, I have discovered that certain geometric relationships must exist or are highly desirable. If most of these relationships are not present, it is not possible for the wrench to effectively grip all sizes of round work which can be placed between the three jaw faces of the wrench. Furthermore, if these relationships are not present, there is not available a substantial uniformity of gripping action for all sizes of round work. Without the relationships which constitute my invention, a swin in aw wrench having the three kinds of jaw faces, that is, two right angular jaw faces and a curved jaw face having a single radius of curvature, a practical wrench would not be made. It would either slip on certain sizes of work or would have too great a crushing force on other sizes or would have other undesirable characteristics.

To have an efficiently operated wrench of the type referred to, there must exist a certain relationship between the axis of the pivot pin I8, indicated on the drawing as P, the center of the curved jaw face 22, indicated as C, the radius of said curved jaw face, indicated as R, and also the relationship of the pivotal axis P of the pivot pin and the jaw face of the swinging jaw member. There should also be a definite relationship of the position of the center C of the curved jaw face with respect to the longitudinal axis of the handle which passesthrough the axis- P of the pivot pin.

In producing a wrench in accordance with my invention, the radius R of thecurved jaw-faceom the end of the handle portion must be between 70 to 85% of the largest diameter of work wliich can be received between thevarious jaws when the swinging jaw is open to its fullest extent.

The pivotal axis of the swinging jaw must;-also= have a predetermined relationship with respect toethe planeof thejaw face 29 of the swinging. jaw-member, said jawface 211 being that face which: is on the longest leg of the jaw member. This relat-ion in the drawings is indicated bythe. letter D-and is-the shortest distance between the pivotal axis P and the plane of thejaw face: 28. I have discovered-that this distance D should be approximately one-half the diameter of the largest round work which can=be received-between the.- jaws when the swinging jaw is in -its maximum open position.

Another relationship which must be present forproper operation of the wrench is the relation shipbetween the center C of the curved jaw face 22 and the pivotal axis P of the swinging jaw member. This relationship should be such that thelargest angle which can exist between the two lines drawn from the center of any size work, which center is indicated on the drawings at W, to thecenter C and to the axis P (this angle is indicated as a on the drawings), must not exceed and mustnot be less than 21. In Figural of the drawing the angle a is shown as the. largest that can exist for the particular size wrench embodying my invention. This angle ais the one that is created for the size of work 23 indicated in Figure I. If a larger size of work is operated upon by. the wrench, then the angle a begins todecrease, as can be seen from Figure 3.

This angle a for the larger diameter work 24 (somewhat smaller than the maximum that can be received between the jaws) being gripped by the wrench isconsiderably smaller than the. angle" a at its maximum as shown. on Figure 1. If a smaller diameter of round work is gripped by the wrench, than that indicated as 23' in Figure 1,. If the relationship between the center C and. the pivotal then the angle a willalso decrease.

axis P'should be such that a maximum angle a couldexist which would'be more than 30 orless than 21, then the-wrench would be ineiiicient in operation as a proper gripping action wouldnot.

exist on work where this maximum angle was created. It would not be possible for the wrench to properly grip round work so that slippage would not be present. When the maximum angle a is greater than 30, slippage occurs and when tween these two points and that longitudinal axis" of the handle of the wrench which passes through the pivot point P. In the drawings this longitudinal axis is indicated by the line PL and the angular relationship of this line to the line drawn between the axis P and the center C should be between 40" and In other words, it is not only necessary that C be located a predetermined distance from P but it should have a certain positionwith respect to the longitudinal center line PL.

In the wrench disclosed as embodying my inventionthereare embodied several new discoveries which I have found to be essential and desirable in constructing an efficient and practical wrench particularly a wrench of the swinging jaw typeini'which 'the swinging jaw 'has right angular jaw faces and: the fixed cooperating jaw has-an outward curiiedrface of a single radius of curvature. These discoveries which involve certain relationships as described need not all be embodied in a single wrench to make it workable although: I have discovered that when all embodieda in the manner: disclosed there is produced the best wrench possible. However, beingaware of: thepossibilitiesof using certain of my discovcries in a manner somewhat different than that disclosed in the same or similar types of wrenches tel-obtain the same results I desire it to be understood: that my invention is not to be limited in scope except as set forth in the appended claim.

What iscl'aimed is:

Ina wrench of the class described, a handle member having a jaw portion provided with an outwardly. curvedjaw face having a single center of? curvature, and-a swinging jaw member having an; inwardly directed extension pivoted to the handle member and provided with jaw faceseach lying. in asin'gle plane and said faces being at rightangles: to each other whereby round work can be receivedand gripped between all three jaw faces, the pivotal axis of the swinging jaw memher being so related to the right" angularjaw fa'ees-and the position of the center of curvature of th'e curved jaw face that the angle which can exist between a line drawn from the center of any size roundwork receivable between the jaw faces to th'ep'ivotal axis and another line drawn from said center tothe single center of curvatur of the engaged-curved jaw face will not be greater than thirty degreesor less than twenty-one degrees, the pivotal axis of the swinging jaw member being so related to the right angular jaw faces and also to the curved jaw face that the largest diameter of round work that can be received between the-jaw faces will be approximately twice the shortest distance between the piv'otal axi's -and the plane in which lies that jaw race of the swinging jaw member which is closest to the pivotal axis.

BERNARD P. KUNZ.

REFERENCES CITED Thefollowing references are of record in the file'ofthis patent:

UNITED STATES PATENTS Number Name I Date 500,025 Montgomery June 20, 1893 800,850 I'rland Oct; 3, 1905 FOREIGN PATENTS Number Country- Date 20,392 Great Britain Sept. 18;].902- 

